Entrainment device for a centrifugal rotor

ABSTRACT

An entrainment device for a centrifugal rotor, which is rotatable about a central rotational axis, having a number of entrainment members arranged in said space for entrainment of entering liquid in the rotation of the centrifugal rotor. The entrainment device comprises a first component, which surrounds the rotational axis and has at least one first projection, which has a radial extension, and a second component, which surrounds the rotational axis and has at least a second projection, which also has a radial extension. The second component is axially insertable in said central space to a position, in which said second projection is present adjacent to said first projection . When the entrainment devices are in place in the central space, a locking member is applicable in releasable engagement with said projection so that the second component is prevented from moving axially relative the first component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Patent Application No.PCT/SE2004/001473 filed on Oct. 14, 2004, which claims priority toSwedish Patent Application No. 0302957-6 filed on Nov. 7, 2003, thesubject matter of these patent documents is incorporated by referenceherein in its entirety.

The present invention relates to an entrainment device for a centrifugalrotor, which latter comprising a rotor body, which is rotatable about acentral rotational axis and delimits a separation chamber, and an inletdevice which is connected to the rotor body for rotation with the sameand which delimits a central space for receiving of liquid, which issupplied to the centrifugal rotor, which central space is incommunication with the separation chamber, the inlet device comprising acentral body arranged centrally in the centrifugal rotor and surroundingsaid space, the central body at its one axial end having an openingwhich communicates with said central space, and an entrainment devicehaving entrainment members arranged in said space for entrainment ofsaid liquid by the rotation of the centrifugal rotor, the entrainmentdevice is in such an engagement to the central body that it is entrainedin its rotation and is prevented to move axially relative the same.

BACKGROUND OF THE INVENTION

Traditionally, an entrainment device of the kind here in question hasbeen in engagement with the central body by means of screws or a nut; tomake possible a change of the entrainment device. Such a change may taketime, e. g. if several screws are used or if the screws or alternativeattachment members are difficult to access. Many centrifugal separatorsare used in the food industry and in biotechnical processes, where highdemands require that all surfaces exposed to a product be able to becleaned very thoroughly. This means that surface contact betweendifferent separate details in a centrifugal rotor is not desirable,since such surface contact often creates gaps, which are difficult toclean. For accomplishment of as good ability to clean as possible,separate details in the centrifugal rotor may be formed such that theyare in with each other at points or along short lines. Threads or seals,which may make cleaning more difficult, should be avoided if possible.

An object of the present invention is to provide an entrainment devicefor a centrifugal rotor, which entrainment device is easy to mount anddismount. Another object of the invention is to provide an entrainmentdevice, which may be cleaned effectively in place in a centrifugalrotor.

SUMMARY OF THE INVENTION

According to the invention these objects may be obtained by means of anentrainment device of the initially mentioned kind, wherein theentrainment device comprises a first component, which surrounds therotational axis and has at least one first projection, which has aradial extension, and a second component, which surrounds the rotationalaxis and has at least a second projection, which has a radial extension,the second component being axially introducible in said central space toa position, in which said second projection is present adjacent to saidfirst projection; and that a locking member is applicable in engagementwith said projection, when said entrainment device is in place in thecentral space, so that the second component is prevented to move axiallyrelative the first component.

According to the invention, if desired, said first component and thecentral body may be connected to each other, but in a preferredembodiment of the invention the first component and the central body areformed in one piece or at least arranged to be fixedly connected to eachother.

The first and the second component may be formed with just one first andjust one second projection, respectively, as indicated above. In thatcase each of these projections may be formed such as an annular flange,which preferably extends substantially perpendicular to said rotationalaxis. However, in a preferred embodiment of the invention the firstcomponent has several first projections, which are distributed aroundthe rotational axis and have a radial extension, leaving firstinterspaces between themselves, and the second component has severalsecond projections, which are distributed around the rotational axis andhave a radial extension, leaving second interspaces between themselves.Possibly, one of the components may have just one projection in the formof an annular flange, whereas the other of the components have severalprojections of the kind just described.

In the case each one of the components have several projections theentrainment device, if desired, may be formed so that said secondprojections are in said first interspace to a position axially at thesame level as said first projections. However, in a preferred embodimentof the invention the entrainment device is formed such that the secondprojections are movable to a position, in which they have axially passedthe first projections at the first component through said firstinterspace.

The locking device may be formed so that after being placed in apredetermined axial position relative said components, it may be turnedso that portions of the same are in engagement with the projections ofthe components in a position in which the locking device prevents thecomponents to move axially relative each other. However, in a preferredembodiment the locking device essentially has the shape of a ring havingportions, which against the influence of a spring force may be movedtowards or away from the rotational axis. With advantage, such asub-annular locking device has an interruption in its extension aroundthe rotational axis, so that different surrounding portions of thelocking device may be conducted to and from engagement with theprojections of the two components.

In the case the projections of the components extend radially towardssaid rotational axis, the locking device may be formed with asubstantially U-shaped cross-section, the opening of which is directedaway from the rotational axis. Thereby, the locking device may bebrought to surround the projections partially and prevent them frommoving axially relative each other.

In the case the entrainment device is formed in a way such that saidsecond projections have been moved to a position, in which they havepassed axially past the said first projections, the locking device maybe in a space axially between the first and second projections. Thelocking device may then have a substantially circular cross-section.

The said projections may extend in different directions. Either, theprojections on the one component are inwardly directed towards therotational axis, whereas the projections on the other component areoutwardly directed from the rotational axis, or all the projections areradially directed in the same direction.

In a particular embodiment of the invention the projections may beplaced axially available outside the central body, but preferably theprojections are placed within the central body and inwardly directed inthe same direction towards the rotational axis. Hereby, substantiallythe entire entrainment device may be arranged within the central body inorder to save space.

As initially stated the entrainment device is to be in engagement withthe central body so that it is entrained in rotation therewith. This maybe provided by a frictional engagement between the entrainment deviceand the central body by keeping the entrainment device by means of thelocking device axially pressed to one or several portions of the centralbody. In order to bring about a forced engagement between theentrainment device and the central body the entrainment device may haveat least a third projection extending away from the rotational axis andarranged to be inserted into a recess formed in the central body.Hereby, the relative rotational motion between the second component andthe central body is effectively prevented.

For obtainment of point contact between separate details included in theentrainment device according to the invention, some or all of thesedetails may be formed with knobs or rounded surfaces arranged so thatthey generate interspaces between adjacent, opposite surfaces.

The aforementioned entrainment devices may be constructed in anysuitable way. For instance, they may be constituted by radially andaxially extending vanes distributed around the rotational axis of therotor. Alternatively, they may be constituted of a stack of with thecentral body and with each other arranged annular discs, giving a morelenient acceleration of incoming liquid than radially and axiallyextending vanes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is to be further described in the following with referenceto the accompanying drawing, in which

FIG. 1 diagrammatically shows a conventional centrifugal rotor in axialsection, provided with a central inlet device for liquid, which is to betreated in the centrifugal rotor,

FIG. 2 in axial section and perspective shows a part of a central inletdevice for a centrifugal rotor, provided with an entrainment deviceaccording to the invention,

FIG. 3 shows a part of the entrainment device according to FIG. 2,

FIG. 4 shows an entrainment body being part of the entrainment deviceaccording to FIG. 2,

FIG. 5 shows an alternative embodiment of the entrainment body, which isshown in FIG. 4,

FIG. 6 shows an alternative embodiment of the part of the entrainmentdevice, which is shown in FIG. 3, and

FIG. 7 shows a part of a central inlet device for a centrifugal rotor,provided with an alternative embodiment of the entrainment deviceaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 there is shown a centrifugal rotor comprising a rotor body 1,which is rotatable around a vertical rotational axis R and whichdelimits a separation chamber 2. For rotation with the rotor body 1 aninlet device 3 is arranged centrally in the same. The inlet device 3delimits a central space 4, which is in connection with the separationchamber 2 through channels 5, which are delimited between the inletdevice 3 and the rotor body 1. Moreover, the inlet device 3 has an inletopening 6 at its upper end that communicates with the space 4. Astationary inlet pipe 7 for liquid, which is to be treated in thecentrifugal rotor, extends from above into the space 4 and opens in thelower part thereof. In the separation chamber 2 a stack of frustoconicalseparation discs 8 is arranged, which are axially separated so that theybetween themselves delimit thin flow paths for through flow of saidliquid. Axially through the stack of separation discs 8 a number ofdistribution channels 9 extends, which are formed by holes in the discs8 located right under each other.

The inlet device 3 comprises a central body 10, which surrounds thecentral space 4, and an entrainment device, which is placed in thecentral space 4. The entrainment device may be formed in different waysand has the function to entrain liquid entering the space 4 through theinlet pipe 7 in the rotation of the centrifugal rotor. In FIG. 1 twodifferent kinds of entrainment members are illustrated, to the leftrespective to the right of the inlet pipe 7. To the left a stack ofannular plane discs 11 is illustrated arranged to surround therotational axis R at some axial distance from each other. To the rightone of several wings 12 is illustrated, which are distributed around therotational axis R and each one extending radially and axially.

A more complete description of the conventional centrifugal rotor inFIG. 1 may be found in U.S. Pat. No. 4,701,158.

In FIG. 2 a first embodiment of an entrainment device according to theinvention is shown. In this entrainment device both an upper part of acentral body 13 (similar to the central body 10 in FIG. 1) and aseparate entrainment body arranged in the space 4 within the centralbody 13 are included. The upper part of the central body 13 may beconsidered as a first component 14 and the separate entrainment body asa second component 15 of the entrainment device.

The first component 14 (i.e. the upper part of the central body 13) hasseveral internal first projections 16 distributed around the rotationalaxis R and leaving first interspaces between themselves. The secondcomponent or the entrainment body 15 has several other projections 17leaving second interspaces between themselves. The projections 16 and 17have a radial extension and are inwardly directed towards the rotationalaxis R.

In FIG. 3 there is shown a central body 13 (somewhat modified) withoutany entrainment body 15 according to FIG. 2, and in FIG. 4 there isshown an entrainment device 15 of the kind as disclosed in FIG. 2.

As realized, the entrainment body 15 (according to FIG. 4) may beinserted in the space 4 from underneath in the central body 13(according to FIG. 3) to a position, in which the projections 17 havepassed and between the projections 16, and are situated axially somewhatabove these, as disclosed in FIG. 2.

In FIG. 2 there is also shown a locking member 18, which is arrangedaxially between the first projections 16 and the second projections 17.The locking member 18 is substantially annular and has a circularcross-section. It has also a discontinuance in its extension around therotational axis (not shown) enable it to be applied between theprojections 16 and 17. In place between the projections 16 and 17 thelocking member 18 keeps the entrainment body 15 relative the centralbody 13, so that the entrainment body 15 cannot fall out of the space 4.

The entrainment body 15 may be formed in different ways. Thus, theactive entrainment members may be formed as, for example, annular planediscs 11 or as radially and axially extending wings 12. FIG. 4 shows anentrainment body 15 provided with wings 12, and FIG. 5 shows anentrainment body 15 provided with discs 11 of the respective kind asillustrated in FIG. 1.

As disclosed in FIG. 4 and FIG. 5 the entrainment body 15 in addition tothe projections 17 has some additional projections 21, which extendradially outwards at the lower part of the entrainment body 15. Theseprojections 21 are intended to extend into corresponding grooves 22formed on the inside of the central body 13, as illustrated in FIG. 2.Through an engagement occurred in this way between the projection 21 andthe central body 13 the entrainment body is prevented from rotatingrelative the central body 13 in the space 4.

In the embodiment of the invention shown in FIG. 2 the first component14 is formed as one part with the central body 13. In FIG. 6 there isillustrated an alternative embodiment of the invention, in which thefirst component 14 is formed as a separate part 19. The separate partmay be connected with the central body 13 in any suitable way. Ifnecessary, separate fastening members may be arranged to keep the part19 to the central body 13. Moreover, the separate portion or thecomponent 19 according to FIG. 6 works in the same way as said firstcomponent 14 according to FIG. 3. If desired, the portion 19 may beprovided with small elevations at its surfaces, which is to be incontact with the central body 13, resulting in point contact instead ofsurface-contact.

In FIG. 7 there is shown an additional embodiment of the invention, inwhich the central body 13 is formed with projections 16, in the same wayas in FIGS. 2 and 3, and the entrainment body 15 is formed withprojections 17, in the same way as in FIGS. 2 and 4. In FIG. 7 there isshown a modified locking member 20, which is annular with adiscontinuance in its extension around the rotational axis R (not shown)and with a U-shaped cross-section, the opening of which is directed awayfrom the rotational axis R.

As seen in FIG. 7 the entrainment body 15 is retained axially relativeto the central body 13 by means of the locking member 20 when theprojections 17 are situated in the interspaces between the projections16 at the same axial level as the latter. The projections 16 as well asthe projections 17 extend radially inwards towards the rotational axis Rand are prevented from moving axially relative each other by the lockingmember 20.

1. An entrainment device for a centrifugal rotor, the rotor comprising:a rotor body, which is rotatable about a central rotational axis anddelimits a separation chamber; and an inlet device which is connected tothe rotor body for rotation with the same and which delimits a centralspace for receiving of liquid, which is supplied to the centrifugalrotor, which central space is in communication with the separationchamber, the inlet device comprising; a central body arranged centrallyin the centrifugal rotor and surrounding said space, the central body atits one axial end having an opening which communicates with said centralspace; and an entrainment device having entrainment members arranged insaid space for entrainment of said liquid by the rotation of thecentrifugal rotor, the entrainment device is in such an engagement tothe central body that it is entrained in its rotation and is preventedto move axially relative the same; the entrainment device comprising afirst component, which surrounds the rotational axis and has at leastone first projection, which has a radial extension, and a secondcomponent, which surrounds the rotational axis and has at least a secondprojection, which has a radial extension, the second component beingaxially introducible in said central space to a position, in which saidsecond projection is present adjacent said first projection; and alocking member in releasable engagement with said projections, when saidentrainment device substantially is in place in the central space, sothat the second component substantially is prevented from moving axiallyrelative the first component.
 2. An entrainment device according toclaim 1, wherein the first component is arranged to be fixedly connectedto the central body.
 3. An entrainment device according to claim 1,wherein the first component and the central body are formed as onepiece.
 4. An entrainment device according to claim 1, wherein the firstcomponent has several first projections, which are distributed aroundthe rotational axis and have a radial extension, leaving firstinterspaces between themselves, and the second component has severalsecond projections, which are distributed around the rotational axis andhave a radial extension, leaving second interspaces between themselves,said locking member being arranged to be in engagement with several ofsaid projections at the respective components.
 5. An entrainment deviceaccording to claim 4, wherein the second component is axially insertablein said central space to a position, in which said second projections isaxially situated at the same level as said first projections at thefirst component in said first interspace.
 6. An entrainment deviceaccording to claim 4, wherein the second component is axially in saidcentral space to a position, in which said second projections havepassed said first projections at the first component in said firstinterspace.
 7. An entrainment device according to claim 6, wherein saidlocking device is substantially annular, is arranged to extend aroundsaid rotational axis and is applicable in a space axially formed betweenthe first and the second projections when the second projections havepassed the first projections.
 8. An entrainment device according toclaim 4, wherein said projections on the one as well as the othercomponent extend radially in the same direction.
 9. An entrainmentdevice according to claim 8, wherein said projections on the one as wellas the other component extend radially inwards towards the rotationalaxis.
 10. An entrainment device according to claim 1, wherein saidlocking device is substantially annular and arranged to extend aroundsaid rotational axis.
 11. An entrainment device according to claim 10,wherein the substantially annular locking device is resilient so thatsurrounding parts of the same are movable towards and away from therotational axis.
 12. An entrainment device according to claim 11,wherein the substantially annular locking device has a discontinuance inits extension around the rotational axis.
 13. An entrainment deviceaccording to claim 12, wherein the substantially annular locking devicehas a substantially circular cross-section.
 14. An entrainment deviceaccording to claim 12, wherein the substantially annular locking devicehas a substantially U-shaped cross-section with the opening directedaway from the rotational axis.
 15. An entrainment device according toclaim 1, wherein said projections are arranged to be placed within thecentral body.
 16. An entrainment device according to claim 1, whereinthe second component comprises at least a third projection extendingaway from the rotational axis and arranged to be inserted into a recessformed in the central body, thereby preventing the relative rotationalmotion between the second component and the central body.
 17. Anentrainment device according to claim 1, wherein said entrainment membercomprises radially and axially extending vanes.
 18. An entrainmentdevice according to claim 1, wherein the entrainment member comprises astack of annular discs placed to said central body and each other.